The load on our routers and the memory use is extremely low. They have been tested to see what happens under certain conditions. Vyatta takes a little memory per connection and we have seen a DDoS killing us because there was no more memory (when we had a low end machine do the work: Dell 1850, 2GB) and we upgraded the machine at that point to rediculous standards. But I will say that there certainly is a place for specialized equipment.
We no longer buy brand computers but have them assembled by our specs. We do not buy support, nor do we have SLAs. We do have enough people who understand and can solve operational issues (i.e. 5). We do tend to replace more stuff that fails to work when updated or has operational issues (like network cards that freeze when under full load, that is you Dell). And we have more hot-spare machines in a second location (good for maintenance, availability on HW failure, contingency plans,