The WRT54G2 is the new design of the old legacy WRT54G router. This is a Wireless-G (802.11g) router that offers slow wireless speeds and caps at 54Mbps. As most wireless routers nowadays support the newer and much faster 802.11n (that caps at 300Mbps or more), the only reason you would want to buy the WRT54G2 is its price. You can find one online for less than $50.
As part of the new design, the WRT54G2 will come withfor both PCs and Macs that is known to be very easy to use.
As far as performance is concerned, the router will offer short range (around 50 feet) and limited throughput speed. If you just need to share Internet and casual home networking, the WRT54G2 will deliver. For heavy Internet usage and online gaming, it's generally a better idea to get a Wireless-N router.
For Linksys Wireless-N routers that have similar design and setup software as the WRT54G2, check this list of reviewed Linksys routers.
The best Wireless-N alternative to the WT54G2, based on price, however, is the. It costs about the same but offers much faster speed and much longer range.