Opinions on Inventor

There is plenty of discussion on 3d cad program selection.. Most highly biased by user experience... But I'll throw in my 2 cents.
I use it and have very little problems with it.. (no more than any other 3d modeling package). All programs have bugs.

My best suggestion is to get 30 day demo versions of both Inventor and Solidworks (and any other one you are looking at) and play around doing something you would typically do in both programs.. Both programs IMO are identical.. However, Solidworks has the greater market share and more compatible/partner program support IMO.

Also, look at what you customers/vendors are using.. Its much easier to share data if you are both on the same program and version.
Remember..3d cad is not backwards compatible so if you are on a newer version your customers,etc... cannot open those native files.

I would base it around your CAM interoperability. Look into SolidCAM or InventorCAM or whatever you may be currently using and choose a package that will communicate the best. It can be a real headache if you choose the wrong package. On the modelling side they are all pretty good, Inv, SWx, SE..

I have used both Solid Works and Inventor. I prefer Inventor only because I have lots of hours in it. I use the professional 2011 now and find the FEA pretty good as only for a first review of the stress analysis while using math and then maybe a test to be completely safe. Inventor is a memory hog. I now use a windows 7, x64, 8 gigs and it run really smooth, no issues. Our new interns learn inventor in a very short time frame.

I think the most important question is what you're using now. Secondary concerns are how big your group is, what kind of parts you make, how much time/money you have to spend on the transition, and why are you switching in the first place.

I've used SWx, Inventor, and Pro/E (now Creo) and they all have highs and lows. Inventor and SWx are more intuitive and easier to use but cannot handle some high-level functionality that Pro/E can. Look up 'trajpar' and see if that means anything to your products. Between SWx and Inventor I prefer SWx, both because it has more interoperability in the industry and because the quality of support and upgrades is several years ahead. Honestly it's better at importing 2D Autocad drawings than Inventor is - Inventor just cheats this by including a seat of Autocad when you buy it.

It's a big step to switch (to/from anything), make sure you take your time and compare function and price apples-to-apples across the different platforms. A side-note, if you post in the Inventor forum you're more likely to find defenders/apologists than anything else.