You don't miss what you've never had. For climb and descent I simply trim the pitch to an airspeed: initially Vy, usually 120+ kts for en route climb, and Vne minus ~5 kts for en route descent. The rate of descent is controlled by throttle if necessary. (Assuming not in moderate turbulence, ATC cooperation, etc..) I find the pitch trim is quite capable of holding IAS.
Pre-select altitude and GL lock features would be nice but not having them is does not create a major workload. FWIW, Aspen told us a couple of years ago that they were going to offer altitude pre-select using their present altitude alert feature but I have not heard anything recently. ISTM, for my current A/P all the Aspen could do would be to engage ALTHLD as the selected altitude is reached so pitch trim would be up to the pilot and the pitch transition might be abrupt if you're attention is elsewhere. (My A/P does alert the pilot that trim is needed.) OTOH, abrupt would be better than overshooting.