Here are some benchmarks from a Netra T1. Using cmd.php (snmpwalk version, PHP is not linked against libsnmp).
Hosts Polled: 35
Average Time to Poll: 2 Minutes
Concurrent Processes: 10
Threads: N/A
Processor Speed: 1000 Mhz
Number of Processors: 1
05/09/2007 11:08:37 AM - SYSTEM STATS: Time:120.3463 Method:cmd.php Processes:10 Threads:N/A Hosts:35 HostsPerProcess:4 DataSources:1257 RRDsProcessed:188
After switching to cactid.
Hosts Polled: 35
Average Time to Poll: 22 seconds
Concurrent Processes: 10
Threads: 10
Processor Speed: 1000 Mhz
Number of Processors: 1
05/09/2007 12:02:30 PM - SYSTEM STATS: Time:22.0534 Method:cactid Processes:10 Threads:10 Hosts:35 HostsPerProcess:4 DataSources:1257 RRDsProcessed:180
Yeah, it took me an hour to install cactid.