I use Draytek Vigor 2800g routers for LAN to LAN VPN's.
I have one in my home office, one in a co-workers home office, and one in the main office. They are all on different subnets (192.168.2.1 - 192.168.3.1 - 192.168.4.1), and use the IPsec tunneling.
The LAN on each site is effectively then joined, and you then have all the computers appearing under microsoft network neighbourhood, can share network resources as if they are local to you etc etc.
Once set up, there is no 'dialling out' to establish a VPN - the routers keep them up all the time.
I have had no downtime or trouble with the service at all.
Some routers also offer this VPN LAN to LAN, such as the cheap Netgear DG's, but I have found they constantly drop connections, and can take ages to re-establish. I also find they cannot use DNS over the VPN, so you have to use IP Addresses. The Drayteks are great as you can use the computers name etc.
Drayteks all the way!
I find you need a decent upload speed on your connections, otherwise opening shares etc can be time consuming.