Alot of it depends on what type of clients you have and what they are doing. The 1230's have a single 802.11b/g radio and I've seen over 30 clients without problems, however - those clients were Symbol scanners that only had a telnet session open running WEP encryption. If your going to have laptop/desktop clients running a stronger encryption I would think it would be much less...
The next generation of AP's, such as the 1242 and 1132, many have dual radios (802.11b/g and 802.11a) in which case if you have a mixture of clients you can see probably 20+ clients on each radio without that much problem. At least assuming you aren't overloading the 100Mb link back to the switch which is unlikely. There are versions of these AP's that only have one radio though, so be cautious. Also, if your environment is only using G or A radios, having both won't do you any good.
The latest generation of AP's running 802.11n you start running into other problems. I'd suspect that you can get the same # of clients on them, but at up to 300Mb per client, you can oversubscribe a 100Mb uplink with a single client and unless you have a gigabit uplinks from the AP to the edge switches and 10Gb further up, you can run into a whole new set of problems.
In almost all cases I'd say you'll get the best ability to monitor the AP's and see which ones are getting overloaded by going with a Unified Wireless infrastructure (ie: using controllers / WCS). This will also allow you to aggressively load-balance APs that are near eachother if desired to get better use of neighboring APs...
