5510's are stable...if you do a few things.
Fun 4.0 code at all costs. Earlier version were very buggy. We had 8 CR's open with Nortel at one point on these things. All were resolved in 4.0.
If you want 1000->100 or 1000->10 to work fine with large TCP window sizes, you will need to make a couple of adjustments.
After updating to 4.0, and doing a default on the switches with the new code, do the following.
-Go in to the command line interface
-Type the following:
config t
qos agent buffer max
qos agent queue-set 4
end
logout
-Reboot the switch(s)
That will completely resolve these issues.
Another thing to think about is setting spanning tree to fast start if you use it.
And for the love of God...don't ever let a user plug a hard network loop in to these things...they absolutely flip. Don't ask how I know. LOL
But if these are in a controlled environment, and the above settings are made, they should not have any issues.
Note that if you have no need for QoS/diffserv, you can upgrade to 4.0.1, which takes the possible 8 queue-sets down to 2 instead of the 8 that are available with 4.0.