Yes, your 100MBps users will love you for it. Although we bought a Netgear 10/100 hub instead because it was a little cheaper. Prices I paid for 100MBps netcards are down to about the $30-75 range and the 5-port hub was about $100. So your cost for 30 PC's would be about $2500 or less to convert everybody. The size of your network warrants the switch to 100MBps. You would have less collisions and retransmision on the network plus the retransmision is 10X faster. Say you save half of your 30 people at least 2 minutes a day for the next year at $10/hour:

30 people/2 * 10 dollars/60 minutes * 2 minutes/day * 5 days/week * 50 work weeks/year = $1250 savings/year

We have to remember that people costs are the big expenses while computer expenses that increase user effectiveness are relatively small in comparison. To reduce response time from 5 secs to 1/2 sec is not just 10x faster, but the user is likely to be 15-20x more productive because of the reduced response time.

All I can recommend is that you don't buy an Office Connect 3C16751 10/100 Dual Speed hub. I have had very limited success getting it to talk to legacy 10 base cards.
Mike