Apple had first mover advantage for refined gui desktop OS'. Heck, it had first mover advantage for desktop pcs as well. Netscape had first mover advantage for commercial web browsers. Ford had first mover advantage for mass produced cars. And apple again had first mover advantage for tablets, full screen smartphones. They all lost out.
Bitcoin has first mover advantage, yes.
Those are pretty bad examples because they generally don't have a network effect (except to a minor extent phones and tablets although the ease of cross platform development has diminished that).
Some examples of early first mover products with network effect would be:
ebay - sure ebay sucks but competitors really couldn't break in because more users = more value and that is hard to beat.
paypal - same thing. people love to bash paypal but surprisingly there is no paypal killer (not talking about Bitcoin just some "better" or less sucky centralized alternative.
gold - picked as commodity money for its properties (divisibility, inert, malliable, etc) however among commodities it is far from the most rare but it lasted due to inertia.
TCP/IP - what a clunked together protocol. horribly ill suited for modern networks (the overhead of small packets of gigabit speed WAN links is insane) but it remains because it would be disruptive to change.
POTS (plain old telephone) - ancient, insanely expensive, low tech and although it is dying (slowly) it lasted decades despite the possibility of something superior replacing it.
All of these benefit from a network effect. The more people using it, the more valuable the system becomes. Bitcoin isn't software, it isn't even a service. Bitcoin is a protocol. There is software than runs the Bitcoin protocol, and there is services which use that software but as a protocol Bitcoin simply needs to be useful enough to lay the foundation.
As far as Bitcoin being nothing but mining. I would point to things like bitpay. bitpay is one of those behind the scenes "boring" companies which unlock value. It allows people to accept Bitcoins easily. That adds to the network effect. If a company can use bitpay to accept Bitcoins easily and other alternatives are harder and almost every potential customer who has "a" cryptocurrency has "the" cryptocurrency then there is little value in accepting alternatives. It reinforces that compounding network effect.
I often get misquoted so to be clear. I am not saying Bitcoin can't be replaced. It certain can. The network effect is a barrier to entry it isn't a force field.The network effect of eBay, Paypal, Gold, TCP/IP and POTS are all MUCH more significant than what Bitcoin has. The biggest hurdle for Bitcoin adoption is getting vendors to accept Bitcoin. That's the biggest hurdle, asking vendors to accept these coins that they can't see or touch, and which has no backing authority. BUT, if they can do get over that hurdle, the challenge to get them to accept a different type of crypto would likely be negligible. If they trust one blockchain, it won't be terribly difficult for them to have trust in another. They just need to be assured that there is community interest in it, that it's not just a pump and dump hatched by a single person who therefore has nearly all the currency.
As far as the services associated with Bitcoin, bitpay, etc. They've done the tough work already, building the service. Adding support for another blockchain is a trivial task at that point. With Bitpay, you send BTC's, it receives them and posts a sale on MtGox, and forwards the funds on to their clients bank account. To have it look up a price for a different coin is trivial, and its just as trivial to post those coins for sale on an exchange. Bitpay's biggest concern would therefore be that if the altcoin they chose has a deep enough market to absorb sales of whichever coin they accept. That's not trivial, but not difficult either. Just the act of announcing support for another cryptocoin would create a lot of interest in that coin and deepen the market just by virtue of the fact that people would know others will be transacting in it.
To me, Bitcoins first mover advantage is therefore close to nil. Every feature, every service that has been or could be created for bitcoin would take only a couple of hours to implement for any other coin. I feel like Bitcoin is a great proof of concept, a nice version 1.0 product. But all it would take would be for an Amazon, a Newegg, TigerDirect or even several of eBay's bigger vendors to say "we now accept BBQCoin" (to just throw out an example), and that coin gains instant credibility, and likely, a much deeper market than Bitcoin does.
