Extensive experience with ProgeCAd and have also used BRICSCAD. BOTH are excellent. BricsCAD gets my nod for STRONG STABLE 3D, and strong stable 2D. B-C departs somewhat from the strict look and feel of AutoCAD, but remains very similar, with the variations being strong options, and very useful. ProgeCAD remains VERY true to the original, with a strict adherence to true fidelity to not only commands and options, but internal dialog boxes, too.
Both are good options. There are others, too. I've hear nothing but good about DraftSIGHT. With licensing for any STRONG workalike hovering at around 10% of AutoCAD, ANY of them are a worthy contender.
I use ProgeCAD for my home projects, which allows me to slip seamlessly into any standard AutoCAD seat at a client office, but any of the ones I've mentioned are STRONG contenders.
Add this to my post on another question- regarding perpetual licensing and surrendering control to the software maker an unacceptable option, a good workalike becomes even more important than just saving $ on a license so that your work remains legal. Add to ALL of this, the move to "Cloud" work and storage (read China hack your designs - anyone?) and you can make an ABSOLUTELY COMPELLING case for switching. The good thing is that when you have a problem, you can still post here, because the solution is probably identical, and that's if the workalike's EXCELLENT support didn't help you solve the problem !
Good Luck !
-C.