Impies can be great beginner gats, I've had 1. Awesome fast (in the right hands). Their main Achilles heel is their weight, and it's efficiency.
If cost is an issue, they can be had very cheaply, and I've seen virtually brand new and modified (i.e. New Designz internals, LPRs, I-Frame etc) Strange and Adrenalin ones up for "half a bag of sand" on here
Good ones are exceptionally low maintenance.
To sum up:
Pro's
1. Cheap as chips at the mo (although buy second hand)
2. Accurate (by volume)
3. Fast (Vision is a must have)
4. Lotta upgrades available. A fully modified one will outshoot an A4 Blender (remember these are still top line NXL ripping machines)
5. Low Maintenance
Con's
1. Heavy
2. Must be heavily modified, so what looks like a brand new bargain, actually requires another monkey on upgrades (Freak systems, I-frames, Delrin Bolts etc etc)
3. You have to listen to numpties telling you to buy Cockers due to their mythical powers. Ignore Pinki, he used to have an X-Mag, Troggy used to shoot Angels and contemplated an A4 (ok he is enlightened now), and Monkey Dug, sucks Belsales willies, so they are not to be trusted on gat advice. Don't get me wrong the half block is an awesome gat, and if you've got the money, should be at the top of your shopping list, but cheap ripping machine it is not (unless you get it on the ML Sponsorship program, although you will be butt whoring in a Bangkok Brothel to get on the team). Fortunately I'm not biased
4. Smartparts is particularly unloved at the moment, and this will affect it's future re-sale value. It's possible that prices have bottomed out, but any patent naughtiness and SP gear could be worthless.
So you pays your money and takes your pick.