I really like the switching tricks that the GS5 can do, especially given that you currently can't get them in any other piece of networking gear for a similar (relatively) low price. As a result, I think that the GS5 will find its way into more than a few networks, even if they don't need wireless bridging. But, as is too often the case, Linksys has released a product with a few problems, some of which need to be immediately addressed.
The GS5's Ingress Rate limiting is broken and should be high on Linksys' bugfix list. Though Egress Rate limiting works fine and can effectively put a kink in clients' download speeds, Ingress Rate limiting is needed to precisely limit bandwidth that could be sucked up by busy uploaders or file sharers. Setting bandwidth hogs' priority to Low is a stopgap measure since at best it limits them to 1/8 of maximum bandwidth using the default Weighted Fair Queue global QoS setting. And changing the global QoS setting to Priority mode isn't really an option, since the resulting bandwidth allocation will probably be too unequal to be really useful.
I also found during my testing that when set to WPA mode and left idle, i.e. no traffic flowing across the wireless bridge, the GS5 disassociated from the WET54G and couldn't reconnect until I power cycled it (the GS5). I didn't determine the exact idle time required, but I'm pretty certain it's longer than 5 but under 30 minutes. This problem is guaranteed to produce frustrated users pretty quickly, so should also be addressed ASAP.
The last problem is documentation. Linksys needs to face up to the fact that if it's going to produce products with advanced features like the GS5 has, they must also produce documentation that helps users understand how to use those features. It's not sufficient to describe the what of a feature in documentation, but "why" and "how" information also needs to be provided. To my mind, ZyXEL's product documentation, though not the best written around, sets a good example of the type of tutorial, "why" and "how" information that Linksys needs to provide.
But once they get these problems straightened out, Linksys should have a real winner on its hands. I'm hoping, though, that the GS5 marks the beginning of general availability of VLAN and QoS features into consumer networking products. You may not know it yet, but you'll be needing at least the QoS features soon!