I recently had the pleasure of playing with Inventor (made by autodesk). I liked it a lot. It was easy to use and the design aspect was more intuitive than UG (I use NX2 mostly).
Are you looking for some sort of analysis software? Look at MCS Adams or any of their other software. It takes a while to learn how to use (my opinion on the UI is that they took the worst parts of UNIX and M$ and combined it all into on crappy interface); however, once you figure it out you'll have access to a lot of good data.
Are you looking for finite element analysis software (google FEA and you'll get more info than I can share here myself)?
Are you looking for lincage design software? There are only a couple of packages available as far as I know that do this--One is called Sam the other is WATT and there is a third call lincages. The last is more of educational use but you could use it to aid in lincage development.
Oh, another CAD package--can't forget this-- I use quite a bit is solidworks. Real easy to use.
If you need software more for manufacturing and design then UG might be good for you. UG has a design suite as well as a manufacturing suite. UG integrates with IDEAS and can be used in conjunction with Adams for design and analysis.
There are probably 47092387409238714 programs available for ME's; however, pointing you toward one is a little tough unless you tell us what you need the software for.
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