Unless an Ursa Major comes waltzing up the street for Trixie to vanquish, I’m not going to believe a word she says! And neither should you! – Spike

The Disclaimer
I'll come right out and say it... I'm not a fan of Trixie, at all. She is a blowhard, she cheats at challenges, she treats Snips and Snails badly (in private) even though she was happy enough with them when they were praising her in front of a crowd, refuses to acknowledge that Twilight stepped in and did what she claimed to be able to do and couldn't, and sneers and runs away instead of thanking Twilight for saving her life (if not her wagon) from the Ursa Minor. And that's only her first appearance.
Now that all the negative stuff is out of the way, I'll accentuate the positive I find in Trixie during the following review, just as if I were her greatest fan... well, that's the idea anyway...

The Plot
Twilight is practicing her magic tricks with help from Spike. Despite his insistence that she is "the most magical unicorn" in Ponyville, she demurs, finding the praise a little embarrassing. Spike's two associates, Snips and Snails, appear and tell them about a powerful unicorn who has come to town.

 They go to the Town Square to find the Great and Powerful Trixie! Now to be fair, the Mane 6 members don't really seem to get the idea of showmanship. It makes sense for a stage musician to use hyperbole to sell their act. However, they immediately pass it off as boasting. And if that were that, their grumbling wouldn't amount to much. Until Rainbow, in an attempt to deflect attention away from a rather boastful comment of her own, boos Trixie. Now Trixie, quite properly, isn't about to take THAT lying down. She proclaims that her magical prowess allowed her to vanquish the dreaded URSA MAJOR! and has a lovely little light show to illustrate (hurray for alliteration!)

 Still met with scepticism, she announces a challenge... "Ponyvillians! Anything you can do, I can do better!" And she points a hoof at Twilight, who is now worried that showing her own skills is going to turn her friends against her. Luckily, AJ is there to step in and accept Trixie's challenge. Unfortunately, her rope skills can be replicated by Trixie, and she ends up trussed. Rainbow Dash meets with a similar humiliation when she creates a rainbow that Trixie turns on her, and zaps her with a cloud to boot.

 Spike then suggests a unicorn v. unicorn bout, but Twilight is too timid and Rarity too dignified to engage in such a tawdry affair. Until Trixie insults Rarity's mane, in which case... it... IS... ON! (Second best meme ever) Rarity creates a beautiful dress out of the curtains, to which Trixie responds by magicking her mane into a literal rat's nest... and worst of all, it's green!

 Finding all her friends vanquished, and herself in the spotlight, Twilight runs away from Trixie's challenge, leaving nopony in Ponyville willing to challenge her.

This calls for a celebratory brushie brushie...

... and an oats smoothie, brought to her by the incredible Annoying Duo, who then pester her to tell them more stories. Well, beating neigh-sayers does make one tired, after all, and she asks them to come back in the morning. They run into Spike, who accidentally put the idea into their heads that they should bring an Ursa to town for Trixie to vanquish and prove her story.

A combined IQ of 1

They find the Ursa, who chases them back to Ponyville. Calling on the intrepid Trixie to help them, they find their hero doesn't have the power to do it, even though she gamely tries. Her efforts do little more than enrage the beast further. Spike finally convinces Twilight that she needs to step up, and she does. Using spells both small and mighty, she pacifies the beast (golly, donchaknow?) and sends it back home to mother... the real Ursa Major, who is quite a bit larger than her Ursa Minor baby.

 With her wagon destroyed, and her reputation as well, Trixie departs Ponyville, leaving Twilight to "punish" Snips and Snails for reckless endangerment of the entire town... with mustaches.

 What I think about the episode:
It's a bit of a mess. The Mane 6's actions are not very laudable, yet they are "proven right" in the story. The less I say about Trixie, the less hate mail I will be getting... I've already said too much, me and Michael Stipe both. The plot is a little too convenient: Snips and Snails happen upon the Ursa Minor in the very first cave they enter. The "punishment" they receive is a laughable one for major property damage and reckless endangerment. The moral "boasting is bad" kind of loses it's punch when you consider that Trixie is doing this for a living rather than just for the sake of it, and that Rainbow was doing plenty boasting of her own.

Final Rating

5 – Celestia Rank: A great episode. It will be re-watched frequently.
4 – Luna Rank: A good episode, but with one or two problems that prevent it from being great.
3 – Spike Rank: An average episode. Positives and negatives are balanced.
2 – Discord Rank: Worth watching once. After that, turn it to stone and put it in the garden.
1 – Nightmare Moon Rank: Send it to the moon!

Stay sunny side up!