This might be a dumb/naive question, and if it is please excuse me :)
I have a brand new machine with the following specs:
In general I use 64-bit Eclipse without problem, but there can be issues around plug-ins such as:
There may be more but those are the ones I've encountered in the past.
Moving to 64-bit gives you access to more addressable memory but it won't speed anything up, in fact it might reduce performance in some cases (but nothing I see as significant to what I do).