A good description of how clientmatch is supposed to work is here: http://www.arubanetworks.com/techdocs/ArubaOS_64x_WebHelp/Content/ArubaFrameStyles/ARM/Client_Match.htm
ClientMatch tries to do three things:
1 - Move dual-band clients to the A band (band-steer)
2 - Load balance clients when too many clients are on a radio (load-balance)
3 - Move clients to another radio when we see that they should be on a
better access point. (sticky client)
#1 occurs fairly quickly to make sure that users end up on the A radio.
#2 starts happening when there are 30 users or more on an access point
#3 happens when (1) an access point sees a user much stronger than the access point the user is on currently (2) that user was seen less than 2 minutes ago.
With regards to #3, if you have more access point density, stickly clients would be detected more quickly and moves would take place more quickly. Also, if the client is not seen that much stronger by the access point we want the client on, no move is made. Lastly, to make sure the user is not moving, the user typically would have to have been on an access point for two minutes before we attempt a "sticky" move. In summary, there are quite a few factors to have to be in play for a client to be move to another access point due to stickiness. We want to make sure the client is not moving, and that the next access point is much better than the previous one. Having more access point density would make sticky moves more efficient.
With that being said, keeping the transmit power of the access point closer to the transmit power of the clients, would make clients make better roaming decisions so that the client match sticky algorithm does not have to move them along.
To see clientmatch moves, use these commands;
(Aruba7640-US) # show ap arm client-match ?
debug Show ARM Client Match debug information
history Show Client Match History
neighbors Neighbor APs seen by all associated clients
pending Show Client Match Pending Moves
probe-report Show list of clients probing in the vicinity of the
AP
restriction-table Show Client Match Restrictions at AP
summary Client Match summary
unsupported Show list of unsteerable clients