I've not done a custodial model broker to broker transfer so can't comment re that, but I do use IBKR as one of my brokers. I find their interface overly complex (probably because their target audience is more traders than buy and hold investors and their feature set is so broad). That said it does what it needs to do. As for FX conversion I just fund directly in AUD and either pre-convert to say USD or just let it auto convert at time of transaction (IBKR's own FX conversion rates are extremely good - I believe basically at spot with miniscule to no FX conversion fees) - basically the only thing you pay is the tiny brokerage

I use IBKR for all international trading. I just put AUD in and let IBKR convert to whatever currency I need as I trade. Spot rate with minimal spread. As far as I'm aware that is the cheapest way to convert the currency.

Only issue with IBKR compared to Australian brokers is the share pricing because we are used to seeing the buy/sell table. I think this is more a function of the markets/exchanges than IBKR and the maybe the times that I trade. Get to know the different types of trades available and the different rules for example extended hours trading and fractional shares can change available order types.

@skaex i was forced to transfer my US stocks from CMC to CommSec, fxxxxx nightmare, ended up selling out and buying back in and taking the tax hit, hopefully better experience for you. The trouble is partly my own, i am terrible at administrative forms and procedures. One mistake and it unravels, good luck

@Dominator, I also use IBKR. Regarding the buy/sell spread, you can buy access to 'Level 2 data' on a monthly basis. It's a bit finicky to locate and then toggle and tick through to the exchanges you want, Nasdaq is separate from NYSE and there's a lot of little exchanges bundled together that I don't fully understand. But I've found it worth it for Microcaps.

@Dominator speak to IBKR directly about what is involved with moving shares onto their platform, I have not done it but have been using IBKR for about 8 years now. The thing you will need to determine is what type of account you have with them, a margin account even if you don't use the margin offers a lot more flexibility. Also if you use a discretionary trust (eg Family trust) to invest with you don't have SEC issues on inheritance or need a whole lot of other forms.

As others have said you get the best FX rates, the trade goes through at the spot rate for a nominal fee (I just tested for A$25k purchase of USD the fee is US$3.07), but if you have a margin account it will process the trade in USD and you will have negative USD cash, which you can address by buying USD and they will just charge the brokerage (which is much cheaper than Australian brokers at US$1 at US$25k).

The platform is complex initially due to all the things you can do, but you only need to know how to do a couple of things to place trades and you have access to algorithmic order types that can help for illiquid (black ice) or volatile markets (time or volume weighted).

Note that it is a US broker and like most US brokers they are not Chess sponsored, so you don't have the normal protections that Australian brokers offer, but this is virtually unique to Australia in any case, so its a risk the rest of the world accepts and is probably the least risky thing about investing in shares.